According to the speedy progress of modern society, the living standard of people is improving day by day and the current scientific technology also makes progress at a tremendous pace, leaving more leisure time and increasing the demand for convenient transportation by developing all kinds of transportation vehicles such as a bicycle, motorcycle, automobile, train, airplane, vessel, etc. For example, it is now a common situation for people with personal taste in enjoying leisure time to own at least one or even several luxury cars. The images of free transportation, comfortable interior decoration, and a wide-range of fanciful daydreams make a car become an incredible enjoyment in everyone's mind, a place for taking refuge and a place for the people to run after their favorite models from every kind of media.
A car is not just the most convenient vehicle in the world. Whether in the form of a sedan, wagon . . . , etc., a car is the best thing for travelling, especially in the hot season in case of no vacant hotel room, in which case the vehicle itself will settle the big headache by serving as a place to sleep.
Even having all kinds of the benefits from vehicles, one problem of car-owners is that someone might forget to turn off the headlights of the vehicle, or turn on the stereo equipment, fan, or even high beam for a long period of time, and force the battery to over-discharge and hence have it burn down or die. Furthermore the huge current caused by a car accident or short circuit might not only burn down the battery but also caused serious fires etc., which tragedies could be prevented if there was a device on the vehicles which had the function of an auto-cut off. Solving this problem of modern people has become a very important topic in present-day living.